The so-called 1U server is a high-availability and high-density low-cost server platform, which is specially designed for the special application industry and high-density computer environment. They can start their own operating systems on a local hard drive, such as Windows NT/2000/2003, Linux, Solaris, etc

U is a unit that represents the external dimensions of a server and is an abbreviation for unit. The detailed dimensions are determined by the us electronic industry association (EIA), an industry group. The purpose of sizing the server is to keep the server in the appropriate size to fit on an iron or aluminum frame. The rack has a fixed screw hole in the server so that it can be numbered against the server's screw hole, which is then screwed in to facilitate the installation of the space required for each server.

The dimensions specified are the server's width (48.26cm = 19 inches) and height (4.445cm multiple). Because the width is 19 inches, the frame that meets this requirement is sometimes called "19 inch frame". The thickness is 4.445cm. 1 u is 4.445 cm

The so-called "1U PC server" is a product that meets EIA specifications and has a thickness of 4.445cm. Products designed to fit into a 19-inch cabinet are commonly referred to as rack servers